Steel frame life span

[Robbos]

Looking for some advice knowing very well it is hard to say with any real precision. But I'll ask none the less.
I've had my Cervelo Prodigy for over a decade now, and I've ridden it pretty regularly, with a very rough ball park of 20 000km on it (there are other bikes in my arsenal!). The paint job, which was never good to begin with is really starting to look rough. I've thought about repainting it, and maybe even getting my local builder to replace the head tube cable guides with down tube stops and maybe a new downtube. With the mileage I described, under 185 pounds of rider, one accident with a car (I took the brunt of the collision), and a downtube bottle mount that once got ever so slightly squished to the left), is it worth putting money into redoing the frame? I love the ride of this bike and I don't need or deserve better. I'm just nervous that investing roughly $200 to give it new life might be wasted if the thin Columbus Foco tubes (main triangle, don't know what the arse end is made of) decide they've had enough. Again, I know it is next to impossible to know when that might be, but feedback from the wizened council of forumites would be appreciated.

[mg2ride]

That frame will likely last you forever.

[sandyrs]

A decade is not enough time to kill a steel frame. See: the thousands of 70s and 80s steel bikes still on the road.

That said, if you're going to pay to get a new downtube welded on there, I'd consider getting a new frame instead and keeping the cervelo as a beater. Maybe keep the geo but go with a different tubeset because variety is the spice of life.

[icepick_trotsky]

I think any bike you've put 20,000 km on is worth your $200 to keep it rolling. Even if it was a Schwinn Varsity.

[purpurite]

You know, back in the 90s there was always loose chatter that steel MTB frames had a finite life span. A number of miles on the clock that would turn the frame immediately into a useless pile of tubes. Not having teh internets or people around me that could set me straight, I sold the best bike I have ever owned with less than 6,000 trail miles on the odo. I felt like I needed to move it before it was worthless.

Serves me right for believing in it as I still am searching for that frame today.



Eventually, the Earth will reclaim everything, but steel bikes will most certainly outlast all of us if they are taken care of properly.

[Robbos]

My other steel bikes with thicker tubes, well I wouldn't have asked the question. But Foco tubes are just so darned thin!

[Mark McM]

Steel (or aluminum or titanium, for that matter) don't just suddenly "give up". The material can fatigue over time, but fatigue can be spotted before it gets to far. Fatigue is due to the slow growth of cracks, which start very, very small, and grow larger over usage/load cycles.

Inspect the frame carefully for the presence of cracks in the tube. Cracks tend to start in the areas of stress concentrations, such as joints and/or corners in the tubing. If there are no cracks present, then the frame should be good to go with no immediate worries. (If there is a crack present, it may be possible to repair - preferably sooner than later, before it grows any bigger).

[icepick_trotsky]

The basics of steel as I understand it, and granted, I'm not a metallurgist, is that there's no such thing as cumulative fatigue or failure for steel.

In other words, steel has a stress threshold after which it will fail, but up to which it will not. Any amount of stress you put on the frame up to that threshold does not result in permanent damage. That is, it doesn't matter how many times you repeat those below threshold stresses -- you can repeat ad infinitum, and it will not cause failure. Repeated minor stresses don't stack or add up to major stresses.

Only stresses above the threshold result in permanent damage and eventual failure, like crashing it.

[Mark McM]

Originally Posted by icepick_trotsky

The basics of steel as I understand it, and granted, I'm not a metallurgist, is that there's no such thing as cumulative fatigue or failure for steel.

In other words, steel has a stress threshold after which it will fail, but up to which it will not. Any amount of stress you put on the frame up to that threshold does not result in permanent damage. That is, it doesn't matter how many times you repeat those below threshold stresses -- you can repeat ad infinitum, and it will not cause failure. Repeated minor stresses don't stack or add up to major stresses.

Only stresses above the threshold result in permanent damage and eventual failure, like crashing it.

Mild carbon steel theoretically has what is called an endurance limit. The endurance limit is the threshold magnitude of cyclic stress below which the material will never fatigue.

However, bike frames are typically not made from mild carbon steel, but are made from high alloy steel, which does not have a true endurance limit. In addition, load cycles in actual use typically are a bit random, so there will still be occasional load above the theoretical endurance limit.

In the real world, all the metals used for bicycle construction (steel, aluminum, titanium) can suffer from fatigue.

[unterhausen]

if you don't let rust kill it, a steel frame will probably last forever. That is, absent any construction flaws. The Italian racing frame I bought in the early '80s lasted me until about 5 years ago. I developed an irrational fear that I had let it rust too much.

Having said that, there are plenty of fatigue failures on steel frames. It's best to monitor for them and also use something like framesaver to combat internal rusting

[johnniecakes]

Not an answer but an option. I have been searching for a prodigy for a long time. IF you decide to retire it let me know. As an opinion I rode my Bill Boston for 20 years till a collision bent the front end more than I wanted to repaìr. The Cora Extra still sees regular duty.

[Tandem Rider]

I would just watch the rust and ride the snot out of it. I have yet to see or experience a catastrophic crash inducing failure on a steel frame, and I've broken a bunch of them.

[Louis]

What some folks are talking about above is the shape of a given material's S-N curve. S = stress, N = cycles to failure.

Basically the S-N curve for most steels tends to flatten out at high cycles, so at stresses below that it can take an infinite amount of cycles. That's called the "endurance limit" of the material.

For AL the curve doesn't flatten out, so if you get enough cycles at some stress level it will fail.

However, more important than whether or not there is an endurance limit is level of the stress itself. Given a high enough stress (due to say, a crash, bad design, or bad manufacturing) anything will fail.

As has been pointed out many times, there are plenty of AL aircraft flying around, some of them quite old.

[rustychisel]

Originally Posted by unterhausen

if you don't let rust kill it, a steel frame will probably last forever. That is, absent any construction flaws. The Italian racing frame I bought in the early '80s lasted me until about 5 years ago. I developed an irrational fear that I had let it rust too much.

Having said that, there are plenty of fatigue failures on steel frames. It's best to monitor for them and also use something like framesaver to combat internal rusting

This. Rust will be the killer, and I think you've had it long enough to rule out obvious construction flaws.

My main riding bike is Reynolds 531db and was made in 1964. That's right, 52 years ago. A race bike for a decade, then a ride to work beater for about 25 years, then after I'd had her for a few years (2nd owner) I had her totally refurbished and fully rebuilt - fixed gear. The ride is sublime and I'm confident she'll be with me until the end.

[Llewellyn]

Originally Posted by rustychisel

My main riding bike is Reynolds 531db and was made in 1964. That's right, 52 years ago. A race bike for a decade, then a ride to work beater for about 25 years, then after I'd had her for a few years (2nd owner) I had her totally refurbished and fully rebuilt - fixed gear. The ride is sublime and I'm confident she'll be with me until the end.

Would love to see a pic.